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由 Aneesh Kumar K.V 提交于
We need to make sure we update the inode bitmap and clear EXT4_BG_INODE_UNINIT flag with sb_bgl_lock held, since ext4_read_inode_bitmap() looks at EXT4_BG_INODE_UNINIT to decide whether to initialize the inode bitmap each time it is called. (introduced by commit c806e68f.) ext4_read_inode_bitmap does: spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group)); if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) { ext4_init_inode_bitmap(sb, bh, block_group, desc); and ext4_new_inode does if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group), ino, inode_bitmap_bh->b_data)) ...... ... spin_lock(sb_bgl_lock(sbi, group)); gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT); i.e., on allocation we update the bitmap then we take the sb_bgl_lock and clear the EXT4_BG_INODE_UNINIT flag. What can happen is a parallel ext4_read_inode_bitmap can zero out the bitmap in between the above ext4_set_bit_atomic and spin_lock(sb_bg_lock..) The race results in below user visible errors EXT4-fs error (device sdb1): ext4_free_inode: bit already cleared for inode 168449 EXT4-fs warning (device sdb1): ext4_unlink: Deleting nonexistent file ... EXT4-fs warning (device sdb1): ext4_rmdir: empty directory has too many links ... # ls -al /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71 ls: /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71: Stale NFS file handle Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu> Cc: stable@kernel.org
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